Film driving mechanism



Feb. 25, 1947. A. G. ZIMMERMAN FILM DRIVING MECHANISM Filed May 26, 1944er//ae G ZAM/PMAM l N V E N TO R.

BY MW ATTOR N EY.

Patentedleb; i941.

signor to Radio Corpora poration of Delaware tion 'of a corapplicationmy ze, 1944, seria; No. scusel Claims. (Cl. ZTI-2.3)

- l Y This invention relates to sound film apparatus, and particularlytoa film feeding or advancing mechanism to provide constant uniform nlmmotion at a specific point in a soundv recorder or Many types oi motionpicture film drives arel known in the art, such as those in which a filmdriving sprocketl advances the film over a. film pulled roller, theroller being mounted ,on a shaft with a fly-wheel or rotary stabilizer.Inl the past, resiliently damped idler or nlm loop rollers between thedrive sprocket and the film pulled drum or roller lhave usuallybeenemployed to prevent speed variations 'of the`drive sprocket fromaffecting the speed *of the film over the drum. These prior systems haverequired considerable space to accommodate the film drive mechanismswith their mechanical filters and the over-al1 unit has,l therefore,been of considerable size. Such units were, and a're satisfactory forrecorders permanently mounted inl fixed positions. To make filmrecorders portable, it-is Vdesirable to reduce their size which makes itneceary' to use all space to the optimum advantage. Thus, it must bedone withoutsacrificing'qualityin the form of, less uniform iihn motionat' the translation points. y

The present invention, therefore, is directed to i a mechanism 'whichprovides a desirable film advancing path betweena closely adjacent drivesprocketl and the film driven roller or drum. The film path is such asto introduce into the film the necessary travel to provide a uniformmotion of the film over the drum on which the sound is recorded. Inbrief, this is accomplished by a pair of flxedly mounted rollers whichprovide a substantially maximum film wrap around the recording drum toobtain the optimum frictionall contact between drum and film, the properdirection of approach for the film ,onto the drive .l 2 4 sprocket andnlm pulled drum to prevent sprocket irregularities from beingintroducedinto the motion of the film over the drum.

AY still further object of the invention is to provide a film pathhaving a plurality of iiim loops intermediate a drive sprocket and afilm pulled rollerlocated closely adjacent one another.

Although the novelffeatures which are believed' to be characteristic 'ofthis invention will be pointed 'out with particularity -in the appendedclaims, vthe manner of its organization and the mode of its operationwill be better understood by referring to the followingdescription readin Vconjunction with the accompanying drawing forming apart hereof, inwhich the single gure is an elevational view of a sound recorderembodying the invention, the figure showing solely the lm path withinthe recorder and the film- Adrive guiding elements for obtaining it. l.Referringnow to the drawing, a casina 5 has mounted on the back wallthereof a rotatable drive sprocket 6 and a illm pulled drum 1, thelatter having either a solid fly-wheel or a rotary stabilizer mounted onthe other end ofits shaft. The film I0 is adapted to be supplied fromsup- 'ply' reel, not shown, and advanced around-the left-hand side ofsprocket 6 while guided by ailxed axis pad roller Il and an adjustableaxis pad roller I2. The film then passes in a loop Il to the film drum 1over a pressure roller i5.

'I'he film is made to almost completely wrap around the roller 1 by afixed axis roller I1 mountsprocket, and the necessary filter film loopsbetween the drive sprocket and film pulled roller.

By directing the film in the manner described hereinafter, a veryuniform film motion is obtainable, and one which is comparable to thatobtainable with the larger stationary equipments.

The principal object of the invention, therefore, is to facilitate theobtaining of a uniform film motion at a translationpoint.

Another object of the invention is to provide a filtered film pathbetween a drive sprocket and film pulled drum located adjacentone'another. A further object of the invention is to provide anVimprovedmethod and means for obtaining a plurality of film loops into ailli between a drive ed on a bracket i9 -doweled to the back wall of thecasingr by `dowels 22 and -23, and fastened to the wall by a screw 2l.From the roller i1. the lm is directed by a. ilxed axis roller I8,mounted on the other end of bracket. I9, to the right-hand side ofsprocket 6 under adjustable axis pad roller 26, the lm leaving; thesprocket under a fixed axis pad roller 21 .to a take-up reel, not shown.

It will be noted that the axes of the rollers I1 and.

I8 lie in a plane at substantiallyy 25 degrees to the plane inwhich the`axes of sprocket and drum 1 lie.

By the dotted lines 30, a drive shaft for a gear 3i which drives a belt32 -forthe take-up reel. is indicated, a worm 34 driving the gear 3| Yand a worm 35 driving thes'procket gear. Shown to the right of thecasing and extending through a Wall thereof is an optical unit 31 foipro;lecting light on theffilm Iii as it passes over the drum 1, thelight beam being modulated. in accordance with sound waves in anywell-knownl manner. The pad roller mechanisms shown at Il, l2. i5. 2l,and 21 are descrlbedin detail and claimed in said sprocket at the point1* i asiduos my copending application, Ser. No. 537,454, led May 26,1944, and will not be further described herein except to state that therollers i2, I8, and

26 are movable away from the sprocket and roller for the purpose ofthreading the illm thereon.

s mentioned above, the lm path provided wraps the 111m almost completelyaround the roller or ydrum l to obtain the greatest friction betweenthe' iilm and drum. Furthermore, the lm is directed onto the sprocket 6substantially tangentially to avoid a iilm `pull on the roller 26 whichwould tend to pull it away fromI the sprocket, the roller 26 beingresiliently held in' operative position by a spring 33. Without therollers I1 and i8 positioned as shown, or with a single roller, lesswrap is obtainable around roller 1, while the iihn would .be pulled bythe sprocket 6 more nearly parallel with a line connecting the axes ofthe sprocket t and the roller 26.

The third advantage of this film path is that there is provided a illmloop at 40 and a second iilm loop at 4i, both of which are locatedbetween the sprocket 6 and theroller l, and both of which aid ineliminating irregularities introduced into the lm by the sprocket 6,since.the loops are in series.. 'I'he large loop i9, of course, preventssuch irregularities from being transmitted to the roller 'i through theother iilm path. This arrangement, therefore, permits the positioning ofthe roller 'l at a minimum distance with respect to the sprocket 6 toreduce the over-all dimensions o a portable recorder, while providing anlm :motion having a, uniformity comparable to that of large permanentequipments.

I claim as my invention: v

1. A lm drive mechanism comprising a drive sprocket, a pad rollerl forholding lm on said sprocket, a illm pulled drum closely adjacent saidsprocket, iixed lrollers for directing said film between said sprocketand said drum to provide a plurality of illm loops in the tensioned pathof said iilm between said sprocket and drum, one of 'said rollers beingpositioned adjacent said sprocket andrpad roller to direct said lmtanlation point comprising a drive sprocket for advancing film inopposite directions on each side thereof, a pad roller on said sprocket,a drinn adapted to be rotated by fllm pulled thereover by said sprocket,said sprocket and drum beine` colsely adjacent one another, a fixedbracket between said sprocket and said drum, and a pair of rollers onsaid bracket, one of said rollers being positioned adlacentsaid drum forproviding a substantially complete wrap of said film around said drum,and the other of said rollers being positioned adjacent said sprocketfor directing 'said' illm substantially tangentially toward saidsprocket at the point of contact of said film with said pad roller.

4. A illm advancing mechanism in accordance with claim 3 in which saidiixed intermediate rollers introduce a pair of lm loops in seriesbetween said sprocket and said drum, and means are provided for forminga third loop in the other film path between said sprocket and said drum.

5. A lm advancing mechanism in accordance with claim 3 in which the axesof said rollers lie in a plane substantially 25 degrees to the plane inwhich the axes of said sprocket and drum lie.

6. Mechanism for obtaining a iilm path be tween a sprocket and a filmpulled drum, com' prising a support for positioning said sprocket anddrum closely adjacent one another, a pad A roller for said sprocket, abracket mounted on said support, a roller for directing film onto saiddrum at a predetermined point on the surface of said drum, and a pair ofrollers mounted on said bracket, one of said pair of rollers beingpositioned adjacent said last-mentioned roller for directing lm ofi' ofsaid drum at a point on the surface of said drum to bring said iilm incontact with substantially all of the surface of gentially ontcsaidsprocket at the point of contact of said film with said pad roller, andmeans for forming ilm into a soft loop on the feed side to said drum..

2. A lm advancing mechanism comprising a sprocket adapted to advance lmson two sides thereof, a pad roller on said sprocket, a lm pulleddrumadapted to have lm pulled thereover by said sprocket, and aplurality of xed rollers intermediate said sprocket and said drum on thetensioned side of the lm path between said sprocket and said drum, oneof said rollers being positioned adjacent said drum for providing asubstantially'maximum wrap of said iilm over said drum, and another ofsaid rollers being positioned adjacent said sprocket for directing saidlm substantially tangentially toward of contact of said lm with said padroller.

3. A lm advancing mechanism for maintain ing a uniform motion of saidillm at a light trans= said drum, and said other roller of said pairbeing positioned adjacent said sprocket for directing illm substantiallytangentially onto said sprocket at the point f contact of said lm withsaid pad roller. A

7. Mechanism in accordance with claim 6 in which the plane of the axesof said pair of rollers lies at an angle of substantially 25 degrees tothe plane of the axes of said sprocket and said drum.

V ARTHUR G. ZIMMERMAN.

REFERENPCES SEITEN) The following referencesare of record in the ille ofthis patent:

UNITED STATES PATENTS Number Name Date 1,780,681 Kellogg Nov. 4, 19301,756,864 Hox'ie Apr. 29, 1930 1,899,571 Kellogg Feb. 28, 1933 2,033,277Elmer et al Mar. 10, 1936 2,248,106 McNabb July 8, 1941 FOREIGN PATENTSNumber Country Date 549,315 British Nov. 16, 1942 39,017 Swedish Feb.11, 1937

